In the diagnosis of a clinical condition in a body tissue or organ, it is known to obtain a number of biopsies from the tissue or organ. For example, in the diagnosis of prostate or breast cancer, a region of the organ is imaged using ultrasonic radiation. The practitioner obtains a 2D image of the region of the organ and then, based on the image, selects a site in the organ from where a biopsy is to be obtained. A cannula is then introduced into the organ to the site and a biopsy is obtained. The cannula is typically integrated with the ultrasound transducer, and the cannula as well as the site in the image from which the cannula is poised to obtain a biopsy is indicated in the image. After obtaining the biopsy, another 2D image of another region of the organ or tissue may be obtained (by moving the ultrasound transducer) and an additional site of the organ or tissue may be selected for obtaining a biopsy. This process may be repeated several times so as to yield a number of biopsies from different sites of the organ or tissue.
In this method of obtaining biopsies, it is difficult for the practitioner to visualize in three dimensions the spatial relationship among the biopsy sites. This is due to the fact that each time the practitioner moves the ultrasound transducer to obtain a new image, the practitioner must remember how the transducer was moved in order to visualize in his mind the spatial relationship between the presently and previously imaged regions and the perspectives from which the regions were imaged. The inability to accurately determinate and record the spatial relationships among the imaged regions often results in biopsies not being obtained from sites where a biopsy should have been obtained.